1. Field of the Invention
The present invention relates generally to a grinding machine, and more particularly to a guard device, for a grinding wheel, which has a front cover which is adjustable depending upon the decrease in the diameter of the grinding wheel.
2. Description of Prior Art
Within a guard device, as disclosed for example with U.S. Pat. No. 3,835,595, issued to S. Oshima et al., a front cover is pivotably mounted upon the upper-front portion of a guard hood through means of a hinge pin, and an adjusting screw shaft is threadedly engaged with the guard hood, and is also rotatably supported upon the front cover so as to adjust the pivotal position of the front cover in correspondence to the diameter of a grinding wheel.
However, due to the fact that the screw shaft is disposed upon one side of the front cover and the guard hood, a bending moment occurs within the hinge pin and the screw shaft when the pivotal position of the front cover is adjusted, and consequently, the rotational movement of the screw shaft becomes very strained, whereby the front cover is difficult to adjust. Furthermore, since the supporting rigidity of the screw shaft disposed along one side of the front cover is considerably small, it is unavoidable that, at the time of breakage of the grinding wheel, the front cover is necessarily inclined and will subsequently be opened by means of the fragments which violently come into contact with the front cover, and therefore, the guard device cannot positively prevent the front cover from opening.
In addition, since the cover of the guard device overlaps, within the operative state, a pivotable side plate which is pivotably mounted upon the guard hood so as to be selectively opened and closed, such is also apt to obstruct the opening motion of the side plate, and consequently, replacement of the grinding wheel from the wheel carrier is also difficult to perform.